I've installed and maintained my own alarm system, I've also fitted the biggest battery I could. We were burgled about ten years ago whilst on holiday (old alarm system with contract) , luckily we were only away a week. The alarm went off and we think they had a quick look around, a few days later it went off again, neighbours could not see anything either time, but the intruders turned the power off the second time obviously intending on coming back when the battery was flat. I've also fitted the loudest internal sirens I could, that will spook them if nothing else.